Conventionally, pressure sensors have been used to detect the pressures of liquids that flow in channels. As the pressure sensors, pressure sensors called a single port type that branches a liquid from a main channel where the liquid flows, to a branch channel, and detects the pressure of the branched liquid are generally used. However, a single port type pressure sensor has the problem that the branched pipe portion becomes a dead volume, and the problem that the liquid staying in the branched pipe portion degrades.
Consequently, a pressure sensor called an inline type that detects the pressure of the liquid flowing in a main channel without branching the liquid to a branch channel from the main channel has been developed. For example, PTL 1 discloses an inline type pressure sensor that includes, as the channels in the housing of the pressure sensor, the first channel that changes a flow from the main channel to the liquid chamber which is provided with a pressure receiving section, the second channel where the flow goes along the liquid chamber, and the third channel that changes a flow direction from the liquid chamber to the main channel.